Abstract

This report summarises the results of the research work on complexation of radionuclides with naturally occurring organic compounds in ground water, part of the Mirage project. In order to improve the techniques and to understand the effect of organics on radionuclide mobility, the following areas have been investigated: (i) alteration of organic material during extraction; (ii) separation of organic material present in groundwater; (iii) assessment of the complexation ability of various organic fractions with radionuclides; (iv) identification, characterisation and quantification of organic material; (v) development of a model to predict a metal binding capacity based on the results of characterisation of unidentified large molecular weight fractions (fulvic and humic acids), and its application. The modelling approach developed has shown promise in dealing with the uncertainties in the properties of humic substances. However, with such a heterogeneous mixture of poorly characterised compounds, much more work is required to unravel the complexities of humic interactions in groundwater.